TPWK vs possible straight

[castigar]

I really really appreciate how you guys reply to my posts. Thanks a lot.

I showed weakness on the river and he bets 50% pot, should I fold or call? I imagine I should fold the river because if he had an A (highly possible) he has hit a straight. But if he has Ax, why did he call the flop bet...unless it's A5 maybe.

PokerStars No-Limit Hold'em, $0.10 BB (5 handed) Hand History converter Courtesy of PokerZion.com

Hero ($13.30)
Button ($24.35)
SB ($12.95)
BB ($10.75)
UTG ($10.15)

Preflop: Hero is MP with T[img]/images/graemlins/diamond.gif[/img], 9[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises to $0.4</font>, Button calls $0.40, <font color="#666666">2 folds</font>.

Flop: ($0.95) 5[img]/images/graemlins/club.gif[/img], 9[img]/images/graemlins/spade.gif[/img], 4[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $0.7</font>, Button calls $0.70.

Turn: ($2.35) 3[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $1.5</font>, Button calls $1.50.

River: ($5.35) 2[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">Button bets $2.7</font>, Hero calls $2.70.

Final Pot: $10.75